SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility

Abstract

The Submillimetre Common User Bolometer Array 2 (SCUBA-2) is an instrument operating on the 15-m James Clerk Maxwell Telescope, nominally consisting of 5120 bolometers in each of two simultaneous imaging bands centred over 450 and 850 µm. The camera is operated by scanning across the sky and recording data at a rate of 200 Hz. As the largest of a new generation of multiplexed kilopixel bolometer cameras operating in the (sub)millimetre, SCUBA-2 data analysis represents a significant challenge. We describe the production of maps using the Sub-Millimetre User Reduction Facility (SMURF) in which we have adopted a fast, iterative approach to map-making that enables data reduction on single, modern, high-end desktop computers, with execution times that are typically shorter than the observing times. SMURF is used in an automated setting, both at the telescope for real-time feedback to observers, as well as for the production of science products for the JCMT Science Archive at the Canadian Astronomy Data Centre. Three detailed case studies are used to: (i) explore convergence properties of the map-maker using simple prior constraints (Uranus -a point source); (ii) achieve the white-noise limit for faint point-source studies (extragalactic blank-field survey of the Lockman Hole); and (iii) demonstrate that our strategy is capable of recovering angular scales comparable to the size of the array footprint (approximately 5 arcmin) for bright extended sources (star-forming region M17).

The JCMT Gould Belt Survey: first results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population

“…The data were reduced using an iterative map-making technique (makemap in smurf, Chapin et al 2013), and gridded to 6 pixels at 850 µm and 4 pixels at 450 µm, as part of the Internal Release 1 GBS data set. The iterations were halted when the map pixels, on average, changed by <0.1% of the estimated map rms.…”

The JCMT Gould Belt Survey: properties of star-forming filaments in Orion A North

“…The bolometer time series data were reduced using the SCUBA-2 iterative map maker (Chapin et al 2013) with the JCMT GBS Internal Release 1 configuration file. A 600 arcsec spatial filter was employed to aid in the removal of sky signal at both 450 and 850 μm.…”

Cold dust emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: dependence on luminosity, obscuration and AGN activity

“…The basic principle of the data reduction is to extract astronomical signal from the time-streams recorded by each bolometer in the SCUBA-2 array and map them on to a two-dimensional celestial projection. We have used the Dynamical Iterative Map-Maker (DIMM) within the Sub-Millimetre Common User Reduction Facility (SMURF; Chapin et al 2013). We refer readers to Chapin et al (2013) for a detailed overview of SMURF, and detailed data reduction steps will be given in Geach et al (in preparation) but describe the main steps here.…”

“…We have used the Dynamical Iterative Map-Maker (DIMM) within the Sub-Millimetre Common User Reduction Facility (SMURF; Chapin et al 2013). We refer readers to Chapin et al (2013) for a detailed overview of SMURF, and detailed data reduction steps will be given in Geach et al (in preparation) but describe the main steps here.…”